Expanding an ADDSI3 into 2 x ADDHI3 does not work

[Paolo Bonzini]

> If I use:
> (define_expand "addsi"

addsi3

>   "{
>   emit_insn (gen_addhi3 (custom_subword(operands[0], 0, SImode),
> 								 custom_subword(operands[1], 0, SImode),
> 								 custom_subword(operands[2], 0, SImode)));
> 	emit_insn (gen_addhi3 (custom_subword(operands[0], 1, SImode),
> 								 custom_subword(operands[1], 1, SImode),
> 								 custom_subword(operands[2], 1, SImode)));

How can this work?  You need something like an adchi3 pattern.

Paolo